requirements_dev -> requirements-dev
diff --git a/tox.ini b/tox.ini
index dbdcaec..4b043ba 100644
--- a/tox.ini
+++ b/tox.ini
@@ -5,7 +5,7 @@
 
 [testenv]
 install_command = pip install --use-wheel {opts} {packages}
-deps = -rrequirements_dev.txt
+deps = -rrequirements-dev.txt
 commands =
     coverage erase
     coverage run -m pytest {posargs:tests}